1. Field of the Invention
The present invention relates to an actinic ray-sensitive or radiation-sensitive resin composition, and an actinic ray-sensitive or radiation-sensitive film and a pattern forming method using the composition. Particularly, the present invention relates to an actinic ray-sensitive or radiation-sensitive resin composition that is suitably used for a production process of VLSIs and high-capacity microchips, a fabrication process of molds for nanoimprint, an ultramicrolithography process applicable for a production process of high-density information recording media, and other photofabrication processes, and relates to an actinic ray-sensitive or radiation-sensitive film and a pattern forming method using the composition. More specifically, the present invention relates to an actinic ray-sensitive or radiation-sensitive resin composition that is suitably usable for microfabrication of semiconductor devices using an electron beam, X-rays, or EUV light, and relates to an actinic ray-sensitive or radiation-sensitive film and a pattern forming method using the composition.
2. Description of the Related Art
In the microfabrication using a resist composition, ultra-micro patterns are required to be formed since integrated circuits are increasingly highly integrated. Therefore, exposure wavelengths tend to be shortened, and for example, lithography techniques that use an electron beam, X-rays, or EUV light instead of excimer laser light are under development.
In electron beam (EB) lithography, it is known that the influence of electron scattering, that is, the influence of forward scattering in a resist film is diminished by increasing an accelerating voltage of an EB. Consequently, in recent years, the accelerating voltage of the EB has tended to be increased. However, if the accelerating voltage of the EB is increased, while the influence of forward scattering is diminished, the influence of the scattering of electrons reflected in a resist substrate, that is, the influence of backward scattering is increased. The influence of backward scattering is particularly great when an independent line pattern having a large exposure area is formed. Accordingly, for example, if the accelerating voltage of the EB is increased, resolution of the independent line pattern is likely to deteriorate.
Particularly, in a case of forming patterns in photomask blanks used for semiconductor exposure, the lower layer of a resist film includes a light-shielding film that contains heavy atoms such as chromium, molybdenum, and tantalum. In this case, the influence of backward scattering caused by reflection from the lower layer of a resist is more marked compared to a case of coating a resist onto a silicon wafer. Consequently, when the independent line pattern is formed on the photomask blanks, there is a possibility that the pattern will be easily influenced particularly by the backward scattering and that the resolution will deteriorate.
Generally, a chemical amplification type positive resist is a photosensitive composition that contains a compound (photoacid generator) generating a strong acid by being irradiated with light and a compound that is turned into an alkali-soluble substance due to the degradation of a hydrophobic acid labile group caused by the catalytic action of the generated acid. In some cases, this photosensitive composition further contains a basic compound to inhibit a dark reaction in an unexposed portion. Due to this basic compound, the acid generated by the influence of scattered electrons is deactivated by a neutralization reaction, whereby film reduction in an unexposed portion can be inhibited. However, if an acetal group having low activation energy of an acid degradation reaction is used as an acid labile group, the degradation reaction of the acid labile group competes with the neutralization reaction between the generated acid and the basic compound. Accordingly, the film reduction of the unexposed portion cannot be completely inhibited, and particularly, the resolution of the independent line pattern deteriorates.
As a method of improving the resolution of the independent line pattern, the use of a resin containing a group that adjusts the solubility of the resin has been examined (for example, see JP2005-157401A). However, this is not fundamental means for solving the above problems and cannot sufficiently satisfy the resolution of the independent line pattern.
The microfabrication using a resist composition is not only directly used for producing integrated circuits but also has been applied for producing a so-called mold structure for imprint in recent years (for example, see JP2004-158287A, JP2008-162101A, and “Fundamentals of Nanoimprint and Technical Development/Application Deployment-Substrate Technique of Nanoimprint and Latest Application Deployment”, edited by Yoshihiko Hirai, Frontier Publishing (June 2006). Accordingly, particularly, even when independent patterns are formed using X-rays, soft X-rays, or an electron beam as an exposure light source, it is important to satisfy high sensitivity, high resolution, and roughness characteristics at the same time, and this is a problem needing to be solved.